High Altitude Airplane Upset - Roll Induced

The short video clip above is an example of a high altitude airplane upset situation that can quickly and unintentionally develop due to a number of factors. This particular scenario is also a great example of why an all-attitude capable jet, such as the APS Marchetti S211 Jet Upset Training Platform shown here, is required to address the full spectrum of airplane upsets, especially at high altitude.

Scenario: High Altitude Airplane Upset

In the scenario-based exercise shown in the video, the airplane gets exposed to clear air turbulence or possibly the wake of another aircraft while on autopilot. The Pilot Flying responds to the unexpected roll-off with a startle-induced incorrect use of rudder to counter roll off, further compounded by an over-application (simulated by the instructor).

Recovery Considerations: High Altitude Airplane Upset

Due to reduced aerodynamic damping at high altitude combined with the swept wing design, the airplane quickly yaw-roll couples propelling the aircraft into a severe flight condition in just a few seconds. In the high altitude environment, there are a diversity of considerations pilots must consider in a developing upset event; role of the autopilot, control response sensitivity, reduced stall angle of attack due to high mach, thrust response, compressibility effects, substantial altitude loss in most upset recovery conditions, aerodynamic damping effects, etc.

As you watch the video, notice how the surprising nature of the upset distracts the recovering pilot from disconnecting the autopilot compounding the recovery process. Although many autopilot systems would disconnect automatically, developing a disciplined approach to automation management is an essential element of all upset training, including high altitude events.

Many Part 25 and Part 23 non-all-attitude capable business jets inappropriately being used for limited scope upset training have maneuvering limitations such as prohibited abrupt rudder input and aileron control throws over 1/2 deflection. This is certainly fine for those models of airplanes for their normal non-upset-training operations. However, as an UPRT training platform, these Part 25 and Part 23 models of business jets have a very limited, or no, safety-assured capability when conducting comprehensive ICAO-compliant Upset Prevention and Recovery Training (UPRT). APS recommends extreme caution to anyone participating in upset training in airplanes like these that are not purpose-built to conduct upset training while assuring substantial safety margins. Moreover, many important training lessons in UPRT occur when the pilot in training inadvertently makes inappropriate control inputs – the training platform, and on-board expert UPRT instructor, must have performance safety margins to allow this learning to take place. Otherwise the instructor must get on the controls immediately to assure safety, thereby missing powerful training opportunities.

Reality Check: High Altitude Airplane Upset

Come on APS, this scenario would never happen … consider this real world event concerning a pilot’s startle-induced over-response to a roll upset due to wake turbulence at high altitude: